第38卷第1期英文摘要

A Review of the Damage Detection and Health Monitoring for Composite Structures

Application of New Denoising Method Based on VMD in Fault Feature Extraction

AbstractVariational mode decomposition(VMD) method is a new time-frequency analysis method. It is an entirely non-recursive model, where the modes are extracted concurrently. However, VMD is sensitive to noise. By making use of this property, a new denoising method based on VMD is proposed. The permutation entropy(PE) is used to determine the amount of noise contained in each variational intrinsic mode function (VIMF), which contains high noise abandoned and low noise smoothed by Savitzky-Golay method. Then, the de-noised signal is decomposed by VMD and the fault features are extracted. The simulation and test results show that the denoising method based on VMD is better than the wavelet transform denoising method and the fault features can be extracted by VMD effectively.

Keywordsdenoising; variational mode decomposition(VMD); permutation entropy(PE); fault feature extraction

Inverse Identification of the Fractional Derivative Model of ViscoelasticMaterials Based on Sweeping Response

AbstractThe fractional derivative model can effectively represent the mechanical behavior of the viscoelastic material in the time and frequency domain. The identification of fractional derivative model is of great importance for viscoelastic composite structure modeling as well as for damping reduction design. A method for identifying the fractional derivative model of viscoelastic materials based on sweeping response of composite structure was proposed. On the basis of considering both the viscoelastic material damping and the remaining equivalent viscous damping, the dynamic equation of viscoelastic composite plate under basement excitation is established and the method for solving the vibration response is also presented. Furthermore, a matching calculation method based on sensitivity is developed to identify the parameters of the fractional derivative model. The cantilevered titanium plate attached with ZN-1 viscoelastic material is chosen to display the proposed method and the parameters of fractional derivative model of this material are obtained. The identified parameters are substituted into the analysis model of the viscoelastic damping plate and the rationality of the identified results is verified by comparing the vibration responses obtained by theoretical calculation and experiments.

Keywordssweeping response; viscoelastic materials; mechanical characteristic parameters; fractional derivative model; parameter identification

Diesel Engine Fault Diagnosis Based on Polar Coordinate Enhancement ofTime-Frequency Diagram

AbstractThe mechanical faults at different parts of a diesel engine are characterized by confusion and non-stationary cycling. A fault diagnose method based on polar coordinate enhancement of time-frequency diagram is proposed. The Gabor transform is applied to achieve the time-frequency feature of the vibration signals; then, the time-frequency features are re-sampled at constant angular interval and transformed to the polar coordinate as enhanced feature of certain areas. Thus, the periodic transient features are enhanced. Polar diagram areas energy of 6 rotation cycle of different diesel engine status is extracted as the fault feature, which is used to train support vector machine (SVM) for the pattern recognition. Experimental result shows that this method highlights the features of five typical engine faults, extracts the fault feature information, and distinguishes different types of wear fault.

Keywordsspolar coordinate; feature enhancement; time frequency diagram; feature extraction

Performance Analysis and Experiment of Electromagnetic RingBalancer During Operation

AbstractHigh-speed CNC machine is a kind of important scientific and industrial equipment. The spindle is a key component of the machine and the automatic balancing is important. An experiment platform has been built to test the properties of an electromagnetic ring balancer. Balancing test which uses influence coefficient method, mainly analyses from the following three aspects: Vibration test on platform itself; effects of rotating speed; effects of the angle of test weight. The experiment used an advanced automatic balancer and classical influence coefficient method. The results show the effects of platform and spindle speed, also get a simple way to get a good influence coefficient. A foundation has been built for two-plane balancing and modal analysis.

Keywordsautomatic balancer; influence coefficient method; vibration; electromagnetic ring

Marginal Spectrum Based on S Transform and Its Application

AbstractIn order to deal with non-stationary and nonlinear vibration, this paper proposes a time-domain marginal spectrum based on the S transform, and the marginal spectrum is given by the time domain vibration signal spectrum analysis method. The simulation signal processing show that the method is more sensitive to impact energy of vibration signal; itis able to extract the characteristic frequency; it can inhibit signal high frequency components and highlight the characteristics of the low frequency components. The successful recognition of the rolling bearing fault shows that the method can extract weak impact characteristic frequency, which further embody the value of the vibration signal spectrum analysis.

KeywordsS transform; time domain marginal spectrum; vibration signal; spectrum analysis

Hybrid Substructure Approach for the Investigation on AerodynamicCharacteristics of Rain-Wind Induced Vibration on Transmission Line

AbstractUnder rain-wind conditions, rivulets often form on the surface of transmission lines, which may cause the rain-wind induced vibration. This kind of vibration seriously threats the safety and stability of the transmission tower-line system. The rivulet′s effect on the original cross-section formation of the transmission lines and its movement are likely to be the cause of the aerodynamic instability. To analyze the mechanism of rain-wind induced vibration on transmission, the transient aerodynamic characteristics of rain-wind induced vibration on transmission line is studied based on the hybrid substructure approach in this paper. The transmission line (including the rivulet) and the flow field are considered as two substructures; the vibration response of the transmission line is measured through wind tunnel tests treated as the moving boundary condition of transmission line in the flow field. Only the flow field around the moving boundary is simulated by the computational fluid dynamics code to obtain the aerodynamic characteristics of rain-wind induced vibration on transmission line. Lastly, the transient aerodynamic lift and drag coefficients are applied to the transmission line, and the comparison is carried out between the vibration responses of the transmission line and experimental results. The research results show that the hybrid substructure approach is an effective approach to obtain the transient aerodynamic characteristics of rain-wind induced vibration on transmission line, and also provides an effective method to obtain aerodynamic characteristics which are inconvenient to be measured in the tests.

Keywordstransmission line; rain-wind induced vibration; hybrid substructure approach; computational fluid dynamics numerical simulation

Vibration Measurement and Control Based on Binocular Vision

AbstractFor the low frequency vibration of a flexible plate, a kind of measurement and control method based on binocular vision is investigated. Visual sensors are used to capture images of the vibration of the flexible plate, and then these images are analyzed by the method of image processing (e.g., image segmentation, stereo matching, etc.) to obtain the vibration information of the flexible plate. The obtained vibration signal is used as feedback control signal. Minimal control synthesis (MCS) control method is adopted to suppress the vibration of the flexible plate. Under the same conditions, the control effect of MCS algorithm and the control effect of proportion differentiation (PD) algorithm is compared. The experimental results demonstrate that the measurement method based on binocular vision and MCS control algorithms are feasible. Also, the control effect of the applied MCS algorithm is superior to that of the PD algorithm.

Keywordspiezoelectric flexible plate; vibration control; binocular vision; minimal control synthesis (MCS) algorithm; image processing; stereo matching

Numerical Study on Vibration Characteristics of Axial Flow CompressorBlade Under Fluid-Structure Interaction

AbstractThe vibration triggered by airflow disturbance is the main reason of compressor blade fatigue failure. Therefore, in this paper, a time domain calculation model of fluid-structure interaction is established to study on the vibration characteristics and to carry out failure analysis of the compressor blade. On the basis of modal test, the vibration analysis model of blade is established and verified by a finite element method. Considering the coupling effect of the gas and the blade, computational fluent dynamics is employed to compute the aerodynamic load on the blade surface under some rated conditions, which is imported to blade vibration analysis model to carry out vibration response analysis. Finally, the blade dangerous working conditions are determined through Campbell diagram, and the blade dynamic stress distribution of these working speeds is to carrying out the blade fatigue failure analysis. The result shows that the peak vibration stress distribution is closely related to the modal shape of the blade. The first order resonance of the blade at the critical speed is the main cause of the blade fatigue failure.

Keywordscompressor blade; vibration characteristic; fatigue; fluid-structure interaction; stress

Deformation Measurement and Analysis for the Large Welding Framesin Manufacturing Processes

AbstractIn order to fully understand how effect of welding and annealing on deformation of frame, the systematic analysis and evaluation methods are proposed by taking 3D average deviation, 3D standard deviation and four corners of the height difference as the evaluation indexes, positioning the large frame as a whole with optical photogrammetric system, and quick acquitting data with laser scanner and processing point clouds data with Geomagic-studio software as well. Here design model is used as reference and a Geomagic-qualify software is used for deformation analysis and evaluation in welding and annealing processes. The research results show that the method above by combining 3D laser scanner with Geomagic can accurately and quickly measure and analyze the deformation of frame in production, which provides a new method for manufacturing quality monitoring. The error analysis indicates that the welding process is the main factor of frame deformation, and the contribution from annealing process is less than 0.58 mm in 3D average deviation. The research results provide a scientific basis to further save annealing time in frame manufacturing and lower the cost of production and energy down.

Keywordsdeformation measurement; bogie frame; Geomagic; laser scanner

Research on Impedance Characteristics of Ultrasonic Motor Based onParallel Resonant Matching

AbstractImpedance characteristic contains important electrical parameters of the ultrasonic motor driving system. Large working current causes the ultrasonic motor (USM) to heat fast, decrease stability and reduce the efficiency of drive system. The impedance characteristic of the system usually affects the working current of the circuit. Currently, the tests of the impedance characteristic of the USM and its driving system are only carried out on a single stator and under low voltage. In this paper, the parallel equivalent circuit model of the USM and its driving system is proposed to obtain the impedance characteristics of the electromechanical system by simulation, and the practical impedance characteristics of the USM are obtained by processing the electric signals through the Fourier decomposition method. The results reveal how the system′s impedance changes with the other parameters. It monotonously increases when the driving frequency decreases; it is reduced when the load torque increases (less than the locked rotor torque). The smaller the resonant matching frequency of electromechanical system, the smaller the system impedance is; the closer the resonance frequency to the resonant frequency of the resonant frequency, the faster the system′s impedance mode increases with the decrease of the driving frequency. Finally, it is summarized that the ideal working frequency of the USM and the matching resonant frequency of the driving circuit should both be slightly larger than the resonant frequency of USM according to the mechanical and electrical impedance characteristics.

Keywordsimpedance characteristics; ultrasonic motor; resonance matching; driving frequency; resonance frequency

De-noising Method for Bearing Vibration Signal Based on CEEMDand Wavelet Semi-soft Threshold

AbstractAiming at how to ensure the integrity of the antifriction bearing fault vibration signal while its noise reduction, a signal de-noising method is proposed using complementary ensemble empirical mode decomposition (CEEMD) combined with wavelet semi-soft threshold, to make the noise reduction of vibration signal of antifriction bearing. First of all, CEEMD signal processing method is used for antifriction bearing fault vibration signal decomposition and different frequency bands of intrinsic mode components (IMFs) can be adaptively obtained according to the signal characteristics. Secondly, the correlation analysis of high frequency signal components with noise pollution is executed, so the high frequency IMFs with higher noise components are achieved and then be handled by wavelet semi-soft threshold noise reduction processing. Finally, the IMFs are recombined after noise reduction processing and the remaining components of signal reconstruction, completing the noise reduction process. Analysis results show that compared with the traditional wavelet threshold de-noising processing method and CEEMD signal de-noising processing method, the proposed method of noise reduction in this paper based on CEEMD and semi-soft threshold wavelet is better, and it can ensure the integrity of the signal.

Keywordsrolling bearing; signal de-noising; complementary ensemble empirical mode decomposition(CEEMD); wavelet semi-soft threshold

Fault Diagnosis of Bearings Combining OEEMD with Teager EnergyOperator Demodulation

AbstractTo extract the weak periodic impulse characteristics of vibration signal measured from the rolling bearing when local defects occur, a fault diagnosis method of rolling bearings combining an optimal ensemble empirical mode decomposition (OEEMD) with Teager energy operator is proposed. The OEEMD method is presented to determine two critical parametersk(the amplitude coefficient of the added white noise) andm(the number of ensemble trials)of the ensemble empirical mode decomposition (EEMD). It combines the correlation coefficient, relative root-mean-square of the error (RRMSE) and signal-to-noise ratio to guide the selection of the two critical parameters. The impulse is separated from the vibration signals of a rolling bearing by OEEMD. Then, the instantaneous amplitude is estimated by Teager energy operator and the characteristic frequency of the impulse component can be acquired from the envelope spectrum of the instantaneous amplitude. In the end, the rolling bearing faults are diagnosed. Both the simulation and experimental data prove The effectiveness of the proposed method.

Keywordsensemble empirical mode decomposition; energy operator; envelope demodulating; rolling bearing; fault diagnosis

Finite Element Model Updating of a Tower Crane IncludingBoundary Condition Uncertainty

AbstractA method is proposed to update the finite element model (FEM) of a tower crane considering the uncertainty of boundary conditions. For tower cranes, the actual dynamic characteristics of the structure are obtained by the vibration testing. First, the FEM of the tower crane considering the uncertainty of boundary conditions is modified. Then, the FEM is updated based on the quadratic response surface method. The non-updated and updated frequencies are compared to the measured frequencies, and the comparison results suggest that the accuracy of the updated results could be improved by considering the influence of boundary conditions. The FEM whose boundary conditions are updated can reproduce modes in the tested frequency range and can predict modes out of the band accurately. These conclusions further show that the method proposed in this paper is feasible and efficient.

Keywordstower crane; model updating; boundary conditions; response surface method

Rotary Type Standing Wave Piezoelectric Actuator for Aperture

AbstractIn order to control and regulate light beam by driving aperture, A new rotary type standing wave piezoelectric actuator is proposed. In the existing PZT actuators with stable performance, always works in composited models of a single PZT oscillator, which a high requirement for manufacturing accuracy is put forward to. The performance and efficiency of the actuators would fall when the coupling effect of the vibration modes deteriorated by the oscillator size change after a long time friction and wear. Aimed to solving the problem and the character of aperture, this piezoelectric actuator is proposed. By using the same model of the same two rod-shaped PZT oscillator, rotary motion of aperture is driven by friction. Prototype machine is designed and manufactured, experimental study is carried out. Under the circumstance of fixing the pre-load pressure at 8N, and adjusting the driving voltage from 200 Vp-pto 400 Vp-p, the rotational speed shows a linear relationship with the driving voltage. The maximum clockwise speed is 75.36 rad/min and the maximum anticlockwise speed is 62.8 rad/min. The resolution of the modal-independent USM is up to 0.34 mrad at the applied voltage of 400 Vp-p. The piezoelectric actuator fulfills the function of driving aperture, characterized by simpler structure, fast response, smooth operation and high precision.

Keywordsaperture; PZT actuator; frequency consistency ; friction and wear

Analysis of Generalized Force and Wind-Induced Responses of Structures Based on High-Frequency Force Balance Wind Tunnel Tests

AbstractThe wind-induced dynamic responses can be analyzed by applying the base bending overturning moment in sway directions and the base torque in the torsional direction measured by the high-frequency force balance (HFFB) technique in wind tunnel. Generally, only the effects of the first mode in each direction (two sway and one torsional directions) can be considered. However, the contribution of the higher order modes cannot be considered. In the present study, a framework for evaluating the generalized force spectra of the higher order modes in the sway and torsional directions is proposed according to the correction method of the generalized force spectra of the ideal mode shape. The data used in the analysis are measured through the HFFB wind tunnel tests. Then, the evaluation of the wind-induced dynamic responses of the aeroealstic model for three typical lattice high rise structures are presented by applying the proposed framework. The calculation results with considering mode shape corrections, higher order mode shape generalized force, and aero-dynamic damping ratios, agree well with those from the wind tunnel tests. This verifies the accuracy of the framework for evaluating the different order mode shape for the generalized force spectra.

Keywordswind tunnel tests; wind effect; generalized forces; high-frequency force balance; mode shape corrections

Measurement and Analysis for the Constitutive Model Parameters of the Rubber Belt

AbstractThe stress responses of the rubber belt with steel rope core under 0°C, 10℃, 20℃, 30℃ and 40℃ are analyzed by employing the dynamic loading stress experiment. Based on the constitutive model of the belt standard solid, the identification equations of the 3 parameters for the belt standard solid are derived by the Fourier series fitting method for the viscoelastic material, and the fitting equations with the temperature variation for the 3 parameters are established. The variation performance with temperature for the 3 parameters are analyzed, the results show that the temperature obviously influences the viscosity coefficientη1and the elastic modulusE1, and the trends are nonlinear, but the influence from the temperature to the elastic modulusE2is small and the trend is linear. Finally, the error analysis of the fitting equations is performed by the experiment, and the maximum error is about 3%. The experiment results prove the accuracy of the identification equations.

Keywordsrubber conveyor belt; viscoelastic; constitutive modeling; parameter identification

Improved Eigensystem Realization Algorithm and Mode Order Determination Based on SVD

AbstractAn improved eigensystem realization algorithm and mode order determination based on singular value decomposition (SVD) is presented. A mode order indicator, called singular value percentage (SVP), is developed according to the weight of selected modes. The indicator is applied to the improved algorithm to determine mode orders in modal identification. The proposed approach includes four main steps: (1) constructing the initial Hankel matrix; (2) eliminating the noise via SVD and obtaining de-noise signal matrix; (3) reconstructing the Hankel matrix by using Cadzow′s algorithm; (4) utilizing the proposed SVP indicator to determine the mode order. Several simulation cases are studied and it is proved that the improved ERA has a better noise resistance ability. The new indicator SVP is effective in mode order determination and false modes elimination. The modal damping ratio can be identified successfully as well. This improved method is also applied to the modal parameter identification of a sedan exhaust system. The effectiveness is proved by comparing identified results with data from LMS system, especially in determining the mode order

Keywordsmodal identification; eigensystem realization algorithm; singular value decomposition; singular value percentage; mode order determination

Rolling Bearing Reliability Evaluation Based on ImprovedLogistic Regression Model

AbstractThe reliability evaluation of the rolling bearing is crucially important in improving the reliability of mechanical equipment and saving maintenance cost. A novel reliability evaluation method is proposed based on improved logistic regression model (ILRM) to solve the problem that the reliability of rolling bearing is difficult to estimate. First, high relative feature set is constructed by selecting the effective features through extracting the time domain, frequency domain and time-frequency domain features of lifetime bearing. Second, the principal components which can accurately reflect the performance degradation process are obtained by principal component analysis. Then, the principle components are used as the covariates of ILRM. Finally, the covariates are brought into ILRM to obtain the reliability of the rolling bearing. The method can be used to extract the effective characteristics of bearing degradation, and can reflect the state of bearing, and eliminate the influence of random fluctuation of signal on the reliability evaluation. The results verified by intelligent maintenance systems full life test of rolling bearing show that the method can accurately evaluate the reliability of rolling bearings.

Keywordsreliability evaluation; improved logistics regression model; fault diagnosis; rolling bearing

Study on Energy Flow of Fruit Trees Under External Excitation Force

AbstractUnder external loads, the vibration energy transfer from excitation position to the branches of fruit trees, and we analyze the effects of fruit tree morphology on energy transfer. Two "Y" type of fruit trees and three branches of fruit trees are chosen as the test samples, and the acceleration signal is fitted to get the acceleration function. Then the speed function can be obtained by the integral of the acceleration function and the kinetic energy of the measuring point on the branches of fruit tree can be also calculated.The kinetic energy we calculated can be regarded as external loads transfer to energy of each point. The value of the acceleration in the branches is accord with the variation of sine function under the sinusoidal excitation, and the branch acceleration signal frequency and the excitation frequency are almost the same. When the energy flowing goes through the bifurcation point, it would be shunted, and more energy move to the side branches with large diameter. The efficiency of transmitting energy in the trunk is higher than the lateral branch; When the excitation frequency is 20Hz, the efficiency of transmitting energy is better, and the maximum of the instantaneous velocity of fruits and amplitude of swing are much larger. So, fruits become easier to fall off.

Keywordsvibration of tree； transmitting energy； morphological structure； excitation frequency

Strain Sensor Based on Rectangle Patched Antenna: Simulation and Test

AbstractWhen a patch antenna is undergoing strain, causing the antenna to deform, its resonance frequency shifts accordingly. Based on this principle, a strain sensor with patched antenna can be used for monitoring strain in structural members. This paper adopts 2.4GHz quarter-wave rectangular patched antennas as strain-sensing units. Firstly, the dimension parameters of patched antennas are determined via HFSSTM, and the resonance frequency shifting of the antennas is simulated when antennas are undergoing the tension strain in length and width direction respectively. Then, the antennas are glued on the surface of aluminum plates along the longitudinal and transverse direction respectively. The resonance frequency of antennas under different stressing level is identified via network analyzer. Both the simulation and test results show there is a good linear relationship between resonance frequency variation and the strain in length direction, while the width variation of the rectangular patched antenna has limited influence on the variation of resonance frequency.

Keywordspatched antenna; strain sensor; resonance frequency；strain transfer efficiency

Crack Growth Monitoring of Horizontal Stabilizer Shaft Based on Lamb Wave

AbstractAs a main bearing part of in-service aircraft, horizontal stabilizer shaft has a slender cavity with variable thickness section. Stress concentration often occurs at the variable thickness section, which results in fatigue crack and thus lead to fatigue fracture. In this paper, an on-line monitoring method of crack depth at variable thickness section based on active Lamb wave is studied. First, the real damage produced by wire cutting is monitored by active Lamb wave, and the response signals are extracted by Shannon continuous complex wavelet transform to eliminate noise. Second, the response signals are analyzed by 4 damage indices emphatically to characterize the rule of crack depth growth. The result shows that the cross-correlation damage index ofA0mode can effectively characterize the rule of crack depth growth best. Finally, the cross-correlation damage factor ofA0mode is used to monitor crack initiation and crack size quantification, which lays the foundation for the on-line monitoring of the horizontal stabilizer shaft. This research has an important application value in realizing the on-line monitoring of the crack in horizontal stabilizer shaft and guiding the service time prolong as well as maintenance of in-service aircraft.

Keywordsactive elastic wave; damage index; fatigue crack; horizontal stabilizer shaft; health monitoring

Monitoring Operating Condition of Pipeline of Pumping Stations Based onPermutation Entropy

AbstractIn order to realize the online monitoring of the working conditions of pipeline of pumping stations, and to ensure the operation of the pumping station safely and stably, a monitoring method based on permutation entropy algorithm for pressure pipeline of pumping station is proposed. This method can give full play to the advantage of permutation entropy algorithm including the simple calculation and the high sensitivity, which can reflect the small changes of the non-linear and non-stationary signal. It can obtain the vibration signal of the pipeline in the pumping station by arranging the sensors in the key parts, which determines the vibration state of the pumping station pipeline by the change of the subsequences entropy in vibration signal. The method of this paper is applied to monitor the operation of the seven pump station pipelines of Jingtai Project Phase II. By setting different operating conditions for instance verification, the results show that in the moment of switching unit the maximum amplitude error of vibration signal subsequence entropy reaches 0.37, and when the unit operate stably, it is only 0.07, this method has high accuracy and reliability in identifying the changes in operating state of the pump pipeline quickly and easily by the change of the entropy. A new idea for the online monitoring of the operating conditions of the pumping station pipeline and a basis for the structural safety diagnosis in the next step are provided by this method, which has good engineering practicability and popularization value.

Keywordsvibration; permutation entropy; signal analysis; pipeline of pumping station; on-line monitoring

Weak Fault Diagnosis Method of Gearbox Based on Improved WaveletDenoising-Teager Energy Operator

AbstractIn order to solve the problem that the characteristic of the weak fault vibration signal of gearbox was not easy to be extracted in the strong noise background, a weak fault diagnosis method based on improved wavelet denoising pretreatment and Teager-kaiser energy operator is presented. The original signal is denoised by the method of wavelet improved threshold function; the signal-to-noise ratio is improved effectively compared to morphological filter method and traditional threshold function method. The denoised signal is composed into several intrinsic mode functions(IMFs) by ensemble empirical mode decomposition (EEMD). The correlation coefficients of each IMF component and the original signal are calculated, and the effective components are screened by combining the spectrum of each IMF component. A time-frequency analysis result of reconstruction signal that used the effective IMF components to get the reconstructed Teager energy spectrum, is compared with a marginal spectrum that used HHT to original signal. The comparison research results show that the proposed method is more effective to extract the week characteristics of gear fault. And the results also prove the proposed method worked.

Keywordsimproved wavelet denoising; ensemble empirical mode decomposition; characteristics extraction; weak fault

APrognosticFusionAlgorithmBasedontheINW-ESN

AbstractTo solve the unsatisfying fault predicting effect of hydraulic pumps based on traditional algorithms, a novel fault fusion predicting method based upon the improved Newman-Watts(INW) is proposed. First, the structure of the reserve pool in traditional echo state network (ESN) is modified, and the INW-ESN fundamental predicting model is established. Neighboring matrix elements are redefined to improve the network performance. Furthermore, the fault fusion prognostic model is proposed. By the employment of Dezert-Smarandache theory (DSmT), the INW-ESN prognostic information and degradation model information are fused to increase predicting accuracy. Finally, the proposed method is verified by the application on the hydraulic pump performance degradation experiment.

Keywordsprognostic; echo state network (ESN); Dezert-Smarandache theory (DSmT); hydraulic pump

ANewTypeofRotaryUltrasonicMotorAppliedtoMicroAirVehicles

AbstractIn this paper a novel high-speed rotary ultrasonic motor based on the out-of-plane flexural vibration mode is proposed. The stator consists of a metal disk and a carbon fiber tube. The carbon fiber tube is bonded to the center of the metal disk, and the carbon fiber tube is used to amplify the vibration amplitude of the metal disk. There are eight piezoelectric plates bonded to the both sides of the metal disk for exciting the stator′s out-of-plane flexural vibration mode. The rotor pressed on the conical surface of the carbon fiber tube can be driven to rotate by the traveling wave propagation via the contact friction force. A three-dimensional finite element model of the ultrasonic motor is built and a numerical simulation is carried out by Ansys software. Trajectories of the contact point can be calculated and the optimal size of the motor can be obtained. Experimental results show that the motor can rotate at the maximum speed of 5 520 r/min when the driving voltage is 350 Vp-pand the driving frequency is 30.9 kHz. The maximum lifting force of the motor after installation of one propeller reaches 14 mN. The experiments show that the maximum rotary speed of the novel motor is higher than the traditional traveling wave rotary ultrasonic motor. The future work is to optimize the structure to improve the performance of this motor for the requirements of micro air vehicles.

Keywordspiezoelectric ceramic; ultrasonic motor; micro air vehicles(MAVs); lift

Fault Diagnosis of Gearbox Based on Improved MOMEDA

AbstractIn critical working conditions, the feature extraction of the composite faults in the gearbox is difficult to be realized. Generally, it is easy for the fault characteristics to escape diagnosis or be misdiagnosed by the improper selection of the method. Due to improper selection of white noise, there will be energy leakage situation when the signal is decomposed by ensemble empirical mode decomposition (EEMD). By calculating the multi-point kurtosis (MKurt) can extract the impact fault cycles, but the tracking effect is not ideal in the strong noise environment. Considering that the accuracy of using multipoint optimal minimum entropy deconvolution adjusted (MOMEDA) to extract fault components is affected by the range of the fault cycle, a self-adaptive fault feature extraction method based on CMF-MOMEDA is proposed in this paper. Firstly, the EEMD is used to decompose the signal into a series of intrinsic mode functions (IMFs) at high and low frequencies. Secondly, the original signal is decomposed into high and low frequency bandsChandCLby the combined use of IMFs with strong a correlation with the original signal and the combined mode function (CMF). Finally, the MKurt spectrums ofChandCLare obtained to extract the fault cycle components, then the appropriate cycle ranges are set and the fault characteristics are extracted by MOMEDA. The feasibility of this method is verified by the application of the fault feature extraction of gearbox.

Keywordscomplex faults； feature extraction； strong noise environment； multipoint optimal minimum entropy deconvolution adjusted； combined mode function

Study on Vibration Characteristics of Continuous Manipulator

AbstractVibration of a working continuum manipulator greatly hinder its extended applications. The vibration, which concerns the manipulator′s elongation and bend, cannot be calculated mathematically, so it is difficult to suppress the vibration. This paper develops a manipulator platform with variable length continuum to measure the acceleration at the end point of the continuum manipulator; the experiments are carried out under different elongations and poses with a given traction length. The vibration characteristic parameters of the continuum manipulator are calibrated by parameter identification method. The first-order damped natural frequency and attenuation coefficient are calibrated under different elongations and poses parameters in order to obtain their functions with the elongationLand bending angleθof the continuum manipulator. When substitute the measured angular velocity into the functions, a complete continuous body arm vibration equation is deduced. Finally, the vibration equation of the end point is verified by experiment. The error is less than 10%.

Keywordscontinuum manipulator; end vibration; vibration characteristics; simplified mode

Wind Speed Identification System Based on Piezoelectric Bimorphs

AbstractIn order to sense external flow field such as the change of wind speed, an integrated system of wind identification components based on piezoelectric bimorphs array is proposed to obtain the flight parameters such as speed and attitude angle. A physical aircraft head model with 4 pieces of wind bimorphs′ sensors is designed as symmetric structure, and the model has little effect on the aerodynamic characteristics. First of all, in the wind tunnel test, the inductive signals of single bimorph are measured by a charge amplifier, NI data acquisition card and Labview virtual instrument analysis software. The least squares algorithm is used to obtain the functional relationship between the inductive voltage (root mean square) of each piezoelectric bimorph and wind speed (vector). Then, the sensing function model of the two variables (the wind velocity and the angle) of wind speed identification system is established to calculate the wind velocity and the angle. The experimental results demonstrate that the design of the wind speed identification of piezoelectric integrated components can realize a two-dimensional measurement of wind speed in the wind tunnel. When the sampling time is 5 s, the sensing accuracies of velocity and angle are smaller than 3% and 3° respectively. Further, the highest resolution can reach 0.5% (velocity) and 0.55° (angle). The integrated components of wind speed identification used in aircraft can quickly sense the wind velocity and direction, the accuracy of sensing function model can meet the requirements of the wind speed identification of external environment. All these lay a theoretical and experimental foundation for the future integration and miniaturization design of aircraft sensor system.

Keywordssensors; piezoelectric ceramics; wind flow; wind speed identification; piezoelectric bimorphs array

Fault Diagnosis of Aircraft Air Conditioning System Based onHierarchy Multi-signal Flow

AbstractBased on the failure mode and effects analysis (FMEA) of the main parts in the air conditioning system, this paper builds the fault model of the air conditioning system by the hierarchy multi-signal flow method. According to the failure analysis, the fault-test dependency matrix for multi-signal flow of air conditioning system is given out. Moreover, fault detection rate (FDR) and fault isolation rate (FIR) of each component are carried out. It′s found that the FDR and FIR, especially the latter parameter, are low. To improve their values, the model is improved by including additional five measurement points. By this way, the FDR is improved from 91.4% to 100%, and the FIR is improved from 32.9% to 83.9%. The results show that the hierarchy multi-signal flow can be used to improve the FDR and FIR, increase the fault diagnosis efficiency, and guide the design of the health management of aircraft air conditioning.

Keywordsfault diagnosis; hierarchy multi-signal flow; failure mode and effects analysis; fault detection rate (FDR)； fault isolation rate (FIR)